What Size Generator to Run a Hot Water Heater

A 10-20 gallon water heater consumes around 1000W - 2000W per hour and can be efficiently powered by a 2500-watt generator. A 30-40 gallon water heater uses 3000W - 4500W and can be run by a 5000-watt generator. However, to understand what size generator is needed to run a hot water heater, you will first need to check its wattage consumption. 

The hot water heater is one of the heavy-duty household appliances. Whether you want to lower your monthly electricity bills or keep the hot water heater running during power outages, consider a solar-powered generator. Jackery Solar Generators are essential home backup solutions that can power most household appliances, including water heaters.

Key Takeaways

• Most electric water heaters require between 1000 and 4500 watts to operate.
• A generator with at least 5000 to 7500 watts of continuous power is recommended to handle both startup surges and sustained operation.
• A mid-sized 2500-watt generator is sufficient if it only powers a small water heater. However, a larger 10,000-watt generator or more is a better choice if other household appliances need power.
• You can consider tankless water heaters, which require less power, to lower electricity bills. You can also choose solar-powered generators, which can supplement energy needs and lower fuel costs.
• Jackery Solar Generators can power water heaters and other essential household appliances to reduce the reliance on the electricity grid.

How Many Watts Does a Hot Water Heater Use

A typical water heater uses between 1000W and 4500W per hour, depending on the size, capacity, brand, and other factors. Generally, the larger the hot water heater tanks are, the more wattage will be needed to heat the water. One of the most accurate ways to determine how many watts your water heater uses is to check the information plate on the unit itself or in the user manual.

How Many Starting and Running Watts Hot Water Heater Use?

When a water heater is turned on, the heating element needs to quickly raise the temperature of the water in the tank. This requires a high initial power draw, or "starting wattage," to achieve that rapid heating. 

Once the water reaches the desired temperature, the heating element cycles on and off to maintain that temperature. This requires a lower, steady power draw, or "running wattage," as it only needs to compensate for the heat lost to the environment through the tank's insulation. 

Here is a table revealing the starting and running wattage of different hot water heaters: 

Note: The appliance's wattage consumption may vary depending on the size, brand, and capacity.

How Much Energy is Needed to Run a Hot Water Heater

The energy needed to run a hot water heater can be calculated by multiplying the appliance's wattage consumption and the time for which you run it. For instance, if you run a 3000W water heater for 1 hour daily, the total daily energy consumption will be 3000Wh. Running the hot water heater every day for a month will require 90kWh. Using the water heater for 5 months every year will require 450kWh.

Types of Generators Suitable for Hot Water Heater

There are three main types of generators for off-grid water heaters: gas, electric, and solar. Let's briefly explain the types so you can make an informed decision: 

Gas Hot Water Generators: These are the most common types of generators. They use gas or propane to heat water. They might be suitable for homes with gas service and commercial buildings that require a reliable source of hot water. However, they produce emissions and are not suitable for indoor use. 

Electric Hot Water Generator: Electric generators are suitable for homes without gas service. They are suitable for residential and commercial buildings where electricity is readily available. However, they are usually less efficient than gas hot water generators. 

Solar Hot Water Generator: Solar-powered generators are the most sustainable options for heating water. They do not produce emissions and can also work during power outages. Jackery Solar Generators are essential home backup solutions that supply steady electricity to crucial household appliances and reduce reliance on the grid. 

What Size Generator to Run a Hot Water Heater

The size of the generator needed to run a hot water heater will depend on the wattage of the appliance and how long you are likely to run it. For instance, a family of five will need more hot water in the winter compared to a family of two. If you want to calculate what size generator to run a hot water heater is needed, here is a step-by-step guide:

Step 1: Note Down the Running and Surge Wattage of the Hot Water Heater

Most hot water heaters consume 1000W—4500W, depending on the size, brand, capacity, etc. The starting wattage is 1.5 - 2 times higher than the running wattage. The power consumption of the hot water heater can typically be found on the appliance itself or in the user manual. 

Let's assume you have a hot water heater that consumes 2000W (running) and 4000W (starting).

Step 2: Add a Safety Buffer

Generators do not operate at 100% capacity, which means it is essential to add a 20% buffer to prevent overheating and overloading issues. 

Minimum Generator Size (Rated Output) = 2000W + (2000W * 0.2) = 2400W 

Minimum Generator Size (Surge Output) = 4000W + (2000W * 0.2) = 4400W

Hence, you will need a generator rated at 2400W and with a 4400W surge output to safely run a hot water heater consuming 2000W.

Step 3: Account for Additional Loads

If you will be adding other appliances with a hot water heater, it is essential to calculate the additional loads. Let's assume you plan to power a hot water heater (2000W), lights (30W), and mini fridge (150W) at the same time. 

Minimum Generator Size (Rated Output) = 2000W + 30W + 150W = 2180W (without any buffer) 

In this case, you will need a 2500-watt generator with a rated output of 2500W and surge power of 5000W to safely run the hot water heater with other loads. 

Similarly, if you want to know what size generator is needed to run a tankless water heater, you can consider investing in a generator with a continuous power output of at least 4500 watts. However, ideally 5000 watts or higher is needed to accommodate the heater's high power draw and other potential loads.

How to Calculate Cost Per Hour Usage of Hot Water Heater

Water heaters are energy-intensive appliances that are used in households. However, unlike an air conditioner that might run for the majority of the day, a water heater runs only for 1 - 2 hours per day. Let's do some math to calculate the cost of running the water heater on grid electricity, diesel generators, and solar-powered generators. 

Note: The calculations assume that the average electricity rate in the USA is $0.1595 and that the 10kW diesel generator operating at 50% load consumes 0.53 gallons per hour. 

As shown in the table above, running a diesel generator to power your hot water heater, consuming 3000W for 2 hours a day, will cost you $11.70, with the expense rising to $351 if used continuously for 30 days. On the other hand, powering your hot water heater with a solar generator keeps costs near zero with only initial investment. If you're looking for a cost-effective and sustainable backup solution, consider Jackery Solar Generators for reliable water heating.

Best Jackery Solar Generators for Hot Water Heaters

Jackery is a leading brand that manufactures solar generators, foldable solar panels, and portable power stations. The Jackery Solar Generators combine portable power stations and solar panels that ensure uninterrupted supply to household appliances during the event of a power outage. Whether you want to reduce your reliance on the electricity grid or power appliances during outages, solar-powered generators have got you covered. Here is one of the best tank and tankless water heater battery backups:

Jackery Solar Generator 5000 Plus

The Jackery Solar Generator 5000 Plus is an essential home backup solution with a large battery capacity that can power most water heaters. The ergonomic design with a pull rod and double wheels ensures easy movement around the home. It also offers dual voltage functionality to power most household appliances working at 120V or 240V. If you want more power, the battery capacity of the solar-powered generator can be easily expanded from 5kWh to 60kWh with additional battery packs. 

Appliances Running Time

• 10 Gallon Water Heater (1000W) = 4.1H
• 20 Gallon Water Heater (2000W) = 2.1H
• 30 Gallon Water Heater (3000W) = 1.4H
• 40 Gallon Water Heater (4000W) = 1.1H
• 50 Gallon Water Heater (5000W) = 48 mins

Customer Review

"The entire 5000 plus bundle arrived within 3 days of ordering it. It is a high-quality product with amazing power generation capabilities. I will be purchasing a second bundle in order to increase our kWh to 60." — S.M.

How Loud Are Different Generators When Running a Hot Water Heater

The noise level of a generator while powering a water heater will vary depending on its type and size. For instance, gas or propane generators emit 50 - 70 dB of noise because they have moving parts. On the other hand, solar generators and inverter generators emit less than 50 dB. 

Jackery Solar Generators do not have moving parts and produce only 30dB of noise, making them suitable for powering household appliances at night.

FAQs About Generators for Hot Water Heaters

Will a 5000-watt generator run a hot water heater?

A 5000-watt generator can run a hot water heater that consumes less power, anywhere around 1000W—4500W. For instance, the Jackery Solar Generator 5000 Plus can power a small hot water heater (1000W) for 4.1 hours, whereas a large hot water heater (4500W) can be used for 54 minutes.

Can a 240 water heater run on 120V?

No, a 240V water heater cannot safely run on 120V. Using the wrong voltage will cause the heating element to produce significantly less heat, which results in very slow or no water heating at all.

Will a 7500-watt generator run a hot water heater?

Yes, a 7500-watt generator can safely run a standard electric hot water heater. However, it is essential to ensure the generator's continuous power rating is sufficient for the heater's wattage requirements.

Conclusion

Hot water heaters are undoubtedly essential household appliances. The answer to the question of what size generator to run a hot water heater will depend on its power consumption and running time. The Jackery Solar Generator 5000 Plus is an essential home backup solution that can power most household appliances, including water heaters. It features dual voltage functionality, ensuring the solar generator can power water heaters at 120V or 240V.